> people living in towns near military bases do not walk up and down the local creeks with Geiger counters any more than they compare soil samples against lists of plausibly leaked toxic chemicals
Not quite true. There are pretty big and active citizen based radiation detection projects [0,1,2,3]. The reason for this is that radiation monitors are quite cheap now and the same people who build weather systems often connect a geiger counter. They're cheap and sensitive since the gov spent so much money trying to detect radiation from space, across borders, and even the smallest traces on people (to detect spies, scientists, etc) all from the Cold War. There are also citizen based communities monitoring water and soil, but this does require more work from the participant. They have to go out and collect samples. Processing can be both expensive and quite a bit of work. This isn't the same as hooking up a $100 device to your weather station, which is a leave and forget type system.
We should note that both these communities are far more active in regions where there are greater dangers (history of nuclear sites/projects, oil facilities, military bases, etc). I'd also like to thank both these communities and others like them. They're all doing important work.
[0]https://www.radiationnetwork.com/
[1] https://jciv.iidj.net/map/
[2] https://cemp.dri.edu/cemp/
[3] https://www.epa.gov/radnet/near-real-time-and-laboratory-dat...